Junction Box for Snap Together Electrical Connections to Photovoltaic Panels

ABSTRACT

A junction box adapted to provide an electrical connection to an electrical wire attached to a photovoltaic panel. The junction box has a lower portion which has an entry slot to allow entry of the wire into the junction box and a raised protrusion over which the wire is bent and formed to be substantially in the same shape as the raised protrusion. The junction box also has a clamp adapted to be attachable to said lower portion, whereby the clamp holds the wire in place for providing the electrical connection. The wire is preferably bus ribbon. The lower portion preferably has an elastic polymeric element disposed between the raised portion and the wire. The raised protrusion may have an elastic polymeric element.

BACKGROUND

1. Technical Field

The present invention relates to electrical connections to photovoltaicpanels and more particularly to a junction box with upper and lowerportions which snap together to achieve the electrical connection.

2. Description of Related Art

A photovoltaic module or photovoltaic panel is a packaged interconnectedassembly of photovoltaic cells, also known as solar cells. Since asingle photovoltaic module can only produce a limited amount of power,commercial installations include several modules or panelsinterconnected in serial and in parallel into a photovoltaic array.Electrical connections are made in series to achieve a desired outputvoltage and/or in parallel to provide a desired amount of current sourcecapability. A photovoltaic installation typically includes the array ofphotovoltaic modules, an inverter, batteries and interconnection wiring.Electronic modules may be integrated with the photovoltaic modules whichperform electrical conversion, e.g. direct current (DC) to directcurrent conversion, electrical inversion, e.g. micro-inverter, or otherfunctions such as monitoring of performance and/or protection againsttheft.

Bus ribbon is a common interconnect that is used to connect photovoltaicmodules. Bus ribbon is made up of a copper ribbon, or flat wire, that iscoated in solder. The solder protects the surface of the copper fromoxidation and provides a layer of solder to form the solder joint. Busribbon is generally 5 mm-6 mm wide, although some applications requirebus ribbon to be more than twice as wide. Bus ribbon may serve as aninput/output to a conventional junction box typically mounted on theback side of the photovoltaic module.

When part of a photovoltaic module is shaded, the shaded cells do notproduce as much current as the unshaded cells. Since photovoltaic cellsare connected in series, the same amount of current must flow throughevery serially connected cell. The unshaded cells force the shaded cellsto pass more current. The only way the shaded cells can operate at ahigher current is to operate in a region of negative voltage that is tocause a net voltage loss to the system. The current times this negativevoltage gives the negative power produced by the shaded cells. Theshaded cells dissipate power as heat and cause “hot spots”. Bypassdiodes are therefore integrated with the photovoltaic modules to avoidoverheating of cells in case of partial shading of the photovoltaicmodule.

Blocking diodes may be placed in series with cells or modules to blockreverse leakage current backwards through the modules such as to blockreverse flow of current from a battery through the module at night or toblock reverse flow down damaged modules from parallel-connected modulesduring the day.

The term “wire” or “electrical wire” as used herein is a piece of metalor other electrically conductive material of any cross-sectional shapeused for carrying electrical currents or signals. Bus ribbon is anexample of an electrical wire used to electrically connect tophotovoltaic panels.

The term “cable gland” as used herein refers to a device used for theentry of electrical cables or cords into electrical equipment and isused to firmly secure an electrical cable entering a piece of electricalequipment.

BRIEF SUMMARY

According to embodiments of the present invention there is provided ajunction box adapted to provide an electrical connection to anelectrical wire attached to a photovoltaic panel. The junction box has alower portion which has an entry slot to allow entry of the wire intothe junction box and a raised protrusion over which the wire is bent andformed to be substantially in the same shape as the raised protrusion.The junction box may have a clamp attachable to the lower portion. Theclamp holds the wire in place for providing the electrical connection.The wire is typically bus ribbon. The lower portion may have an elasticpolymeric element disposed between the raised protrusion and the wireand or the raised protrusion may have an elastic polymeric element.

The junction box may have an upper portion including a terminal. Theterminal connects to an electrical load. The terminal is adapted to beapplied under pressure onto the wire, thereby conforming the terminal tobe of substantially the same shape as the raised protrusion. The upperportion typically has a fastener which closes the upper portion to thelower portion under pressure. The terminal is typically spring loaded.The electrical load may be a direct current (DC) to DC converter, a DCto alternating current (AC) inverter, a DC motor or a battery. The upperportion preferably has a seal which is positioned between the upper andthe lower portions. The seal is adapted to seal under the same pressurewhich effects the electrical connection between the terminal and thewire. The upper portion typically includes a diode connected to theterminal. The diode may be either a bypass diode or a blocking diode.The upper portion may be an electronic module connected to the terminal.The upper portion preferably has a cable gland.

According to embodiments of the present invention there is provided amethod to provide a connection to a photovoltaic panel. A wire, e.g. busribbon, which connects electrical to the photovoltaic panel is passedthrough an entry slot of a lower portion of a junction box. The busribbon is bent over a raised protrusion provided in the lower portion ofthe junction box. The bus ribbon is formed to be substantially the sameshape as the raised protrusion. The bus ribbon is typically clamped ontothe protrusion of the lower portion of the junction box.

An upper portion of the junction box is inserted into the lower portionof the junction box and while inserting a terminal is loadedcompressively onto the bus ribbon. The compressive loading may includespring loading. Additionally while inserting, the upper portion issealed to the lower portion of the junction box. The terminal istypically conformed to the shape of the protrusion while electricallyconnecting to the bus ribbon between the terminal and the protrusion. Anelastic polymeric material is typically inserted between the protrusionand the wire.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 shows a partial view of the back side (i.e. non photovoltaicside) of a photovoltaic panel according to an embodiment of the presentinvention.

FIG. 2 shows a lower half of a junction box assembly according to anembodiment of the present invention.

FIG. 3 a which shows a junction box assembly with clamp according to anembodiment of the present invention.

FIG. 3 b shows a partial cross sectional view of a wire ribbon mountedin a lower junction box assembly with a clamp according to an embodimentof the present invention.

FIG. 4 shows a method according to an embodiment of the presentinvention.

FIGS. 5 a and 5 b show isometric views of upper an junction box assemblyconnected/inserted into a lower junction box assembly according to anembodiment of the present invention.

FIGS. 5 c and 5 d show isometric views of the underside of an upperjunction box assembly according to an embodiment of the presentinvention.

FIG. 5 e shows a cross section view of an upper junction box assemblyinserted into a lower junction box assembly according to an embodimentof the present invention.

FIG. 5 f shows area A shown in FIG. 5 e in greater detail according toan embodiment of the present invention.

FIG. 5 g shows a method according to an embodiment of the presentinvention.

FIGS. 6 a and 6 b show an upper junction box assembly inserted into alower junction box assembly according to another embodiment of thepresent invention.

FIG. 6 c shows an underside isometric view of an upper assemblyaccording to an embodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below to explain the presentinvention by referring to the figures.

Before explaining embodiments of the invention in detail, it is to beunderstood that the invention is not limited in its application to thedetails of design and the arrangement of the components set forth in thefollowing description or illustrated in the drawings. The invention iscapable of other embodiments or of being practiced or carried out invarious ways. Also, it is to be understood that the phraseology andterminology employed herein is for the purpose of description and shouldnot be regarded as limiting.

By way of introduction, embodiments of the present invention aredirected to enable an interconnection of photovoltaic panels with cablesand/or photovoltaic panels with electronic modules such as alternatingcurrent (AC) inverters or direct current (DC) to DC converters with aminimal use of hand tools while providing electrical isolation andhermeticity.

Reference is now made to the drawings. FIG. 1 shows a partial view ofthe back side 104 (i.e. non photovoltaic side) of a photovoltaic panel100 according to an embodiment of the present invention. bus ribbons are102 located on back side 104 of panel 100 and provide electricalconnections to internal photovoltaic cells of panel 100.

Reference is now made to FIG. 2 which shows a lower half of a junctionbox assembly 218 according to an embodiment of the present invention.Assembly 218 is typically attached to back side 104 of panel 100 at thetime of manufacture/assembly of panel 100. Assembly 218 may be made orcast as one piece, in the form of a plastic injection molding. Assembly218 has support rails 216, retainer clip 214 and lower part 210 ofjunction box.

Reference is now also made to FIGS. 5 a and 5 b which shows isometricviews of upper junction box assembly 500 connected/inserted into lowerjunction box assembly 218 according to an embodiment of the presentinvention. Assembly 500 has a lid 504 which when removed shows an upperterminal assembly 528 fixed into lower assembly 218 using screws 530.Upper terminal assembly 528 after being inserted into lower assembly 218provides complete electrical isolation of the electrical connection ofupper assembly 528 with the lower assembly 218. Lid 504 provides acosmetic appearance and/or further level of isolation. Attachedmechanically and electrically to upper terminal assembly 528 iselectronic module 524. Electronic module 524 is attached mechanically topanel 100 using support rails 216 and retainer clip 214. Electronicmodule 524 has cable glands 526 which allow a cable entry intoelectronic module 524 where the cable may be terminated insideelectronic module 524.

Referring back to FIG. 2, support rails 216 may be made from one pieceof plastic as part of an injection molding process or as separate parts.Support rails 216 may be made from spring metal which may be plasticcoated. Support rails 216 provide the correct distance between module524 and backside 104 of panel 100. Support rails 216 also providesupport for module 524 along with retainer clip 214. Retainer clip 214may also be made from spring metal which may be plastic coated or madefrom one piece of plastic as part of an injection molding process.

Reference is now also made to FIG. 3 a which shows junction box assembly218 with clamp 300 according to an embodiment of the present invention.Clamp 300 is preferably attached to the bottom side 210 a of junctionbox 210 with an adhesive, by screws through hole pillars 212 or by theinsertion of upper junction box assembly 500 (FIG. 5 b) and thetightening of screws 530 into threaded pillars 212.

Referring back to FIG. 2, junction box 210 has gland apertures 220 toaccommodate embodiment 600 and through hole pillars 212. Through holepillars 212 are typically used to attach junction box 210 to backside104 of panel 100. Through hole pillars 212 may also be used to attachclamp plate 300 to the bottom side 210 a of junction box 210.

Junction box 210 has a slot 210 b where bus ribbons 102 are passedthrough and are placed into the inside of junction box 210. Bus ribbons102 are typically bent and formed over raised protrusion 208. Raisedprotrusion 208 may have additionally a rubber or elastic material 206placed in-between protrusion 208 and bus ribbon 102.

Reference is now made to FIG. 3 b which shows a partial cross sectionalview 302 of wire ribbon 102 mounted in lower junction box assembly 218with clamp 300 according to an embodiment of the present invention.Cross sectional view 302 shows bus ribbon 102 clamped by clamp 300 overelastic material 206 and protrusion 208. One of two gaskets 310 (forexample an “O” ring), is shown between bottom side 210 a of junction box210 and clamp 300. Gasket 310 provides a level of sealing against theingress of water and/or dust into panel 100. Additionally the undersideof clamp 300 may be coated with an elastic material to provide sealingbetween the elastic material and bus ribbon 102. bus ribbon 102 passesthrough slot 210 b of junction box 210. bus ribbon 102 continues througha hole in backside 204 of solar panel 100 and is connected to thephotovoltaic cells inside panel 100. Protrusion 208 is typically formedby an indentation on bottom side 210 a of junction box 210. Bottom side210 a of junction box 210 is located and may be attached on backside 204of solar panel 100.

Reference is now made to FIG. 4 which shows a method 401 according to anembodiment of the present invention. Typically, assembly 218 is attachedto backside 104 of panel 100 at the time of manufacture/assembly ofpanel 100 whilst ensuring bus ribbon 102 is passed through entry slot210 b of junction box 210 (step 403). With bus ribbon 102 located insidejunction box 210 as a result of step 403, bus ribbon 102 is bent overelasticated material 206 and protrusion 208 (step 405). After beingbent, bus ribbon is then formed (step 407) to take substantially theshape of protrusion 208 and/or elasticated material 206. The bending(step 405) and forming (step 407) of bus ribbon 102 is then held firmand clamped into place (step 409) in junction box 210 using clampingplate 300. Clamp 300 is preferably attached to the bottom side 210 a ofjunction box 210 with an adhesive, by screws through hole pillars 212 orby the insertion of upper junction box assemblies 500 and 600 (notshown) and the tightening of screws 530

Reference is now made to FIGS. 5 c and 5 d which show isometric views ofthe underside of upper junction box assembly 500 according to anembodiment of the present invention. Upper junction box assembly 500 haselectronic module 524 with lid 532, when lid 532 is removed thecomponent side of electronic circuit board 542 is shown. Circuit board542 is typically a direct current (DC) to DC converter or a DC toalternating current (AC) inverter. Termination of interconnecting cableson circuit board 542 is provided by insertion of interconnecting cablesinto cable entry glands 526. Upper terminal assembly 528 has mountingthrough holes 540 which along with screws 530 (not shown) are used aspart of the insertion and retention of assembly 500 into lower junctionbox assembly 218. Upper terminal assembly 528 also has terminals 536which provide an electrical connection between circuit board 542 and thecurved portions 536 a of terminals 536. An indented portion of assembly528 houses curved portions 536 a of terminals 536 and typically theremay be an elastic material placed between assembly 528 and curvedportions 536 a. Sufficient flexibility and movement of curved portions536 a typically allows curved portions 536 a to conform around the bentand formed portion wire ribbon 102 when upper junction box assembly 500inserted into lower junction box assembly 218.

Reference is now made to FIG. 5 e which shows a cross section view ofupper junction box assembly 500 inserted into lower junction boxassembly 218 according to an embodiment of the present invention. Area Ashows an electrical connection between upper junction box assembly 500inserted into lower junction box assembly 218. Upper junction boxassembly 500 includes further; electronic module 524 with lid 532 andelectronic circuit board 542. Lid 532 rests and is held by support rails216 along with module 524 held by retainer clip 214. Terminal 536provides the electrical connection between circuit board 542 andconnection to photovoltaic cells in panel 100 (not shown) via theelectrical connection between upper assembly 500 inserted into lowerassembly 218.

Reference is now made to FIG. 5 f and FIG. 5 g which show area A shownin FIG. 5 e in greater detail and a method 501 respectively according toan embodiment of the present invention. Area A shows details of theinsertion (step 505) of upper junction box assembly 500 inserted intolower junction box assembly 218 to form an electrical connection betweencircuit board 542 and connection to photovoltaic cells in panel 100 (notshown). The electrical connection is formed between curved portion 536 awhich may be spring loaded and bus ribbon 102. Curved portion 536 a isheld by assembly 528. Curved portion 536 a is connected to circuit board542 via terminal 536. Sealing of lower assembly 218 is provided bygaskets 310 which provide a level of sealing against the ingression ofwater and/or dust into aperture 210 b by using clamp 300. Sealingbetween upper assembly 500 and lower assembly 218 is provided by gaskets534. Further sealing of upper and lower assemblies by lid 504.Protrusion 208 is formed as a part of the bottom side 210 a of junctionbox 210. In between protrusion 208 and bus ribbon 102 is elasticmaterial 206.

Reference is now made to FIGS. 6 a and 6 b which show upper junction boxassembly 600 inserted into lower junction box assembly 218 according toanother embodiment of the present invention. Upper junction box assembly600 inserted into lower junction box assembly 218 does not make use ofsupport rails 216 and retainer clip 214 only junction box 210 of lowerassembly 218. Clamp 300 in junction box 210 is preferably attached tothe bottom side 210 a of junction box 210 with an adhesive, by screwsthrough hole pillars 212 or by the insertion of upper junction boxassembly 600 and the tightening of screws 630 into threaded pillars 212.Upper assembly 600 after being inserted into lower assembly 218 providescomplete electrical isolation of the electrical connection of upperassembly 600 with the lower assembly 218. Lid 602 provides a cosmeticappearance and/or further level of electrical isolation and sealing.Assembly 600 has cable glands 626 which allow a cable entry intoassembly 600 where the cable may be terminated inside assembly 600.

Reference is now made to FIG. 6 c which shows an underside isometricview of upper assembly 600 according to an embodiment of the presentinvention. Curved portions 636 a are typically held by an indentedportion of assembly 600. An elastic material may be placed betweenassembly 600 and curved portions 636 a. Sufficient flexibility andmovement of curved portions 636 a typically allows curved portions 636 ato conform around the bent and formed portion of wire ribbon 102 whenupper junction box assembly 600 is inserted into lower junction boxassembly 218. Curved portions 636 a are connected to one end of a bypassdiode 642 via terminal 636. Bypass diodes 642 are typically connectedbetween terminals 636. Sealing between upper assembly 600 and lowerassembly 218 is provided by gasket 634. Further sealing of upper andlower assemblies may be by lid 602. Upper assembly 600 after beinginserted into lower assembly 218 is held in place by screws 630 (notshown) which go through holes 640. Cables are typically passed throughand are held by glands 626 and terminated in clamp 638. Clamp 638 istypically spring loaded and is moved by an insertion of a screwdriver toreveal an aperture. The aperture receives an insertion of a conductorprovided by a cable which is inserted into gland 626. The removal of thescrewdriver causes the aperture to close which clamps the conductor inclamp 638 and a connection of the conductor with terminal 636 isestablished.

Reference is now made again method 501 shown in FIG. 5 g with respect toupper assembly 600 according to an embodiment of the present invention.Upper assembly 600 inserted (step 505) into lower junction box assembly218 to form an electrical connection between cables terminated in clamp638 and connection to photovoltaic cells in panel 100 (not shown). Theelectrical connection is formed between curved portion 636 a (which maybe spring loaded) and bus ribbon 102. Insertion of upper assembly 600into lower assembly 218 further provides sealing between upper assembly600 and lower assembly 218 by gasket 634. Further sealing between upper600 and lower 218 assemblies is provided by lid 602.

The definite articles “a”, “an” is used herein, such as “a terminal”, “ajunction box” have the meaning of “one or more” that is “one or moreterminals s” or “one or more junction boxes”.

Although selected embodiments of the present invention have been shownand described, it is to be understood the present invention is notlimited to the described embodiments. Instead, it is to be appreciatedthat changes may be made to these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined bythe claims and the equivalents thereof.

1. A junction box adapted to provide an electrical connection to anelectrical wire attached to a photovoltaic panel, the junction boxcomprising: a lower portion including: an entry slot to allow entry ofthe wire into the junction box; and a raised protrusion over which thewire is bent and formed to be substantially in the same shape as theraised protrusion.
 2. The junction box of claim 1, further comprising: aclamp attachable to said lower portion, whereby the clamp holds the wirein place for providing the electrical connection.
 3. The junction box ofclaim 1, wherein said lower portion further includes an elasticpolymeric element disposed between said raised portion and the wire. 4.The junction box of claim 1, wherein said raised protrusion includes anelastic polymeric element.
 5. The junction box of claim 1, furthercomprising: an upper portion including a terminal, wherein said terminaloperatively connects to an electrical load, wherein said terminal isadapted to be applied under pressure onto the wire, thereby conformingsaid terminal to be of substantially the same shape as said protrusion.6. The junction box of claim 5, wherein the wire is bus ribbon.
 7. Thejunction box of claim 5, wherein said terminal is spring loaded.
 8. Thejunction box of claim 5, wherein said electrical load is selected fromthe group consisting of: a direct current (DC) to DC converter, a DC toalternating current (AC) inverter, a DC motor and a battery.
 9. Thejunction box of claim 5, wherein said upper portion includes a fastenerwhich closes said upper portion to said lower portion under saidpressure.
 10. The junction box of claim 5, wherein said upper portionincludes a seal between said upper and lower portions, wherein said sealis adapted to seal under the same pressure which effects the electricalconnection between said terminal and the wire.
 11. The junction box ofclaim 5, wherein said upper portion includes a diode connected to saidterminal.
 12. The junction box of claim 11, wherein said diode isselectively either a bypass diode or a blocking diode.
 13. The junctionbox of claim 5, wherein said upper portion includes an electronic moduleconnected to said terminal.
 14. The junction box of claim 5, whereinsaid upper portion includes a cable gland.
 15. A method to provide aconnection to a photovoltaic panel, the method comprising: passing awire through an entry slot through a lower portion of a junction box;bending said wire over a raised protrusion provided in said lowerportion of said junction box; forming said wire to be substantially thesame shape as said raised protrusion; and clamping said wire onto saidprotrusion of said lower portion of said junction box
 16. The method ofclaim 15 further comprising: inserting an upper portion of said junctionbox and during said inserting compressively loading a terminal to saidwire, and conforming said terminal to the shape of the protrusion whileelectrically connecting to the wire between said terminal and theprotrusion.
 17. The method of claim 15, further comprising: inserting anelastic polymeric material between the protrusion and wire.
 18. Themethod of claim 15, wherein said wire wire electrically connects to saidphotovoltaic panel.
 19. The method of claim 15, wherein during saidinserting, sealing said upper portion to said lower portion of thejunction box.
 20. The method of claim 16, wherein said compressivelyloading includes spring loading